Ionic liquids

ABSTRACT

The present invention relates to compositions of matter that are useful as ionic liquids. The compositions of the invention are based on an N-substituted pyrrolidinone, said pyrrolidinone having a pendant ammonium cation that is separated from the pyrrolidone ring by a variable length alkyl spacer.

FIELD OF INVENTION

This invention relates to compositions of matter that are useful asionic liquids.

BACKGROUND OF THE INVENTION

Ionic liquids are liquids composed of ions that are fluid around orbelow 100 degrees C. (Science (2003) 302:792-793). Ionic liquids exhibitnegligible vapor pressure, and with increasing regulatory pressure tolimit the use of traditional industrial solvents due to environmentalconsiderations such as volatile emissions and aquifer and drinking watercontamination, much research has been devoted to designing ionic liquidsthat could function as replacements for conventional solvents.

Ionic liquids generally consist of salts of organic cations, such as theN-alkylpyridinium, 1,3-dialkylimidazolium, tetraalkylammonium,tetraalkylphosphonium and trialkylsulfonium cations. Demberelnyamba,Shin and Lee (Chem. Commun. (2002) 1538-1539) describe petroleum-derivedionic liquids based on N-vinyl-γ-butyrolactam having the Formula:

wherein X⁻ is a bromide or tetrafluoroborate anion.

Described herein are novel compositions based on pyrrolidinones that areuseful as ionic liquids. The compositions of the present inventionexhibit unique properties due to separation of the ammonium cation fromthe pyrrolidinone ring using a variable-length alkyl spacer group.

SUMMARY OF THE INVENTION

The present invention relates to a composition of matter of the Formula:

wherein:

-   -   (i) Z is —(CH₂)_(n)—, wherein n is an integer from 2 to 12;    -   (ii) R², R³ and R⁴ taken independently are H, —CH₃, —CH₂CH₃ or        C₃ to C₆ straight-chain or branched monovalent alkyl; and    -   (iii) A⁻ is an anion selected from the group consisting of        [BF₄]⁻, [PF₆]⁻, [SbF₆]⁻, [CH₃CO₂]⁻, [HSO₄]⁻, [CF₃SO₃]⁻,        [HCF₂CF₂SO₃]⁻, [CF₃HFCCF₂SO₃]⁻, [HCClFCF₂SO₃]⁻, [(CF₃SO₂)₂N]⁻,        [AlCl₄]⁻, [CF₃CO₂]⁻, [NO₃]⁻, [SO_(4]) ²⁻, Cl⁻, Br⁻, I⁻, and F⁻.

In one embodiment of the invention, Z is —(CH₂)_(n)—, wherein n is aninteger from 2 to 6. In another embodiment of the invention, the anionis [PF₆]⁻, [HCF₂CF₂SO₃]⁻, [CF₃HFCCF₂SO₃]⁻, [HCClFCF₂SO₃]⁻ or[(CF₃SO₂)₂N]⁻.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to novel compositions based onN-substituted pyrrolidinones, said pyrrolidinones having a pendantammonium cation that is separated from the pyrrolidone ring by avariable length alkyl spacer. Compositions of the invention should beuseful as solvents and, perhaps, as catalysts for many reactions,including aromatic electrophilic substitution, nitration, acylation,esterification, etherification, oligomerization, transesterification,isomerization and hydration. Use of pyrrolidinone-based compositions ofthe present invention is also advantageous because the pyrrolidinonescan be readily prepared from levulinic acid or levulinic acidderivatives obtained from the hydrolysis of inexpensive renewablebiomass feedstock.

Definitions

In this disclosure, a number of terms and abbreviations are used. Thefollowing definitions are provided.

By “ionic liquids” is meant organic salts that are fluid around or below100 degrees C.

By “alkyl” is meant a monovalent radical having the general FormulaCnH_(2n+1). “Monovalent” means having a valence of one.

By “hydrocarbyl” is meant a monovalent group containing only carbon andhydrogen.

By “catalyst” is meant a substance that affects the rate of the reactionbut not the reaction equilibrium, and emerges from the processchemically unchanged.

By “homogeneous acid catalyst” is meant a catalyst that is molecularlydispersed with the reactants in the same phase.

By “metal catalyst” is meant a catalyst that is comprised of at leastone metal, at least one Raney® metal, compounds thereof or combinationsthereof.

By “promoter” is meant an element of the Periodic Table that is added toenhance the physical or chemical function of the catalyst. The promotercan also be added to retard undesirable side reactions and/or affect therate of the reaction.

By “metal promoter” is meant a metallic compound that is added toenhance the physical or chemical function of a catalyst. The metalpromoter can also be added to retard undesirable side reactions and/oraffect the rate of the reaction.

“Selectivity” refers to the weight percent of a particular reactionproduct in the total product weight (including the weight of unreactedreactants).

“Conversion” refers to the weight percent of a particular reactant thatis converted to product.

The term “pyrrolidinone” is used synonymously with “pyrrolidone”; theterm “pyrrolidine-2-one” is used synonymously with “2-pyrrolidone”.

As used herein, the term “biomass” refers to any cellulosic orlignocellulosic material and includes materials comprising cellulose,and optionally further comprising hemicellulose, lignin, starch,oligosaccharides and/or monosaccharides. Biomass may also compriseadditional components, such as protein and/or lipid. According to theinvention, biomass may be derived from a single source, or biomass cancomprise a mixture derived from more than one source. Biomass includes,but is not limited to, bioenergy crops, agricultural residues, municipalsolid waste, industrial solid waste, sludge from paper manufacture, yardwaste, wood and forestry waste. Examples of biomass include, but are notlimited to, corn grain, corn cobs, crop residues such as corn husks,corn stover, grasses, wheat, wheat straw, hay, rice straw, switchgrass,waste paper, sugar cane bagasse, sorghum, soy, components obtained frommilling of grains, trees, branches, roots, leaves, wood chips, sawdust,shrubs and bushes, vegetables, fruits, flowers and animal manure.

The present invention relates to compositions of matter of the Formula:

wherein:

-   -   (i) Z is —(CH₂)_(n)—, wherein n is an integer from 2 to 12;    -   (ii) R², R³ and R⁴ taken independently are H, —CH₃, —CH₂CH₃ or        C₃ to C₆ straight-chain or branched monovalent alkyl; and    -   (iii) A⁻ is an anion selected from the group consisting of        [BF₄]⁻, [PF₆]⁻, [SbF₆]⁻, [CH₃CO₂]⁻, [HSO₄]⁻, [CF₃SO₃]⁻,        [HCF₂CF₂SO₃]⁻, [CF₃HFCCF₂SO₃]⁻, [HCClFCF₂SO₃]⁻, [(CF₃SO₂)₂N]⁻,        [AlCl₄]⁻, [CF₃CO₂]⁻, [NO₃]⁻, [SO₄]²⁻, Cl⁻, Br⁻, I⁻, and F⁻.

In one embodiment of the invention, Z is —(CH₂)_(n)—, wherein n is aninteger from 2 to 6. In another embodiment of the invention, the anionis selected from the group consisting of [PF₆]⁻, [HCF₂CF₂SO₃]⁻,[CF₃HFCCF₂SO₃]⁻, [HCClFCF₂SO₃]⁻ and [(CF₃SO₂)₂N]⁻. In still anotherembodiment, Z is —(CH₂)_(n)—, wherein n is an integer from 2 to 6, andthe anion is selected from the group consisting of [PF₆]⁻,[HCF₂CF₂SO₃]⁻, [CF₃HFCCF₂SO₃]⁻, [HCClFCF₂SO₃]⁻ and [(CF₃SO₂)₂N]⁻.

The composition may be synthesized from a pyrrolidine-2-one of theFormula:

wherein:

-   -   (i) Z is —(CH₂)_(n)—, wherein n is an integer from 2 to 12; and    -   (ii) R² and R³ taken independently are H, —CH₃, —CH₂CH₃ or C₃ to        C₆ straight-chain or branched monovalent alkyl.        Synthesis of N-hydrocarbyl Pyrrolidine-2-one:

The pyrrolidine-2-one may be synthesized by contacting levulinic acid oran ester thereof with a diamine of the Formula R²R³N-Z-NH₂ in thepresence of hydrogen gas and a catalyst according to Reaction (I):

wherein:

-   -   (i) Z is —(CH₂)_(n)—, wherein n is an integer from 2 to 12;    -   (ii) R² and R³ taken independently are H, —CH₃, —CH₂CH₃ or C₃ to        C₆ straight-chain or branched monovalent alkyl; and    -   (iii) R⁵ is H, —CH₃, —CH₂CH₃ or C₃ to C₈ straight-chain or        branched monovalent alkyl.

In another embodiment, the pyrrolidine-2-one may be synthesized bycontacting a salt of levulinic acid, such as ammonium levulinate, with adiamine of the Formula R²R³N-Z-NH₂ in the presence of hydrogen gas and acatalyst.

In one embodiment of the invention, Z is —(CH₂)_(n)—, wherein n is aninteger from 2 to 6. In another embodiment, R⁵ is ethyl.

The pyrrolidine-2-one formed in Reaction (I) can be synthesizedaccording to the methods and conditions taught in U.S. Pat. No.6,818,593 (hereinafter to referred to as '593). Although '593 describesthe synthesis of 5-methyl-N-alkyl-2-pyrrolidinone from the reductiveamination of levulinic acid with nitro compounds, the methods andconditions taught in '593 (column 2, line 66 through column 7, line 21)can be utilized for the process described by Reaction (I) whereinlevulinic acid, a salt thereof, or an ester thereof and a diamine areconverted to a pyrrolidine-2-one in the presence of hydrogen gas and acatalyst.

Levulinic acid may be obtained from biomass. For the conversion ofbiomass to levulinic acid, biomass may be contacted with water and anacid catalyst in a train of one or more reactors, preferably underpressure at elevated temperature. This basic process is described, forexample, in U.S. Pat. No. 5,608,105, U.S. Pat. No. 5,859,263, U.S. Pat.No. 6,054,611 and U.S. Patent Application 2003/0233011. Generally,cellulose in the biomass is converted to levulinic acid and formate inone or more reactors. Levulinic acid produced from biomass may also beconverted to levulinic acid esters for example as described in U.S.2003/0233011A1 through the reaction of levulinic acid with olefins.

For the synthesis of pyrrolidine-2-ones according to Reaction (I), amolar ratio of diamine to levulinic acid, a salt thereof, or an esterthereof of from about 0.01/1 to about 100/1 is preferred at the start ofthe reaction; a molar ratio of about 0.3/1 to about 5/1 is furtherpreferred at the start of the reaction. A temperature range of fromabout 25 degrees C. to about 300 degrees C. is used for the reductiveamination reaction; a temperature range of from about 75 degrees C. toabout 200 degrees C. is preferred. A pressure range of from about 0.3MPa to about 20.0 MPa is employed for the reaction; a pressure range offrom about 1.3 MPa to about 7.6 MPa is preferred. The reaction may beperformed in a non-reacting solvent medium such as water, alcohols,ethers, and pyrrolidones. Alternatively, the excess of diamine can alsoact as the medium of the reaction.

The principal component of the catalyst useful for Reaction (I) isselected from metals from the group consisting of palladium, ruthenium,rhenium, rhodium, iridium, platinum, nickel, cobalt, copper, iron,osmium; compounds thereof; and combinations thereof.

A chemical promoter may augment the activity of a catalyst. The promotermay be incorporated into the catalyst during any step in the chemicalprocessing of the catalyst constituent. The chemical promoter generallyenhances the physical or chemical function of the catalyst agent, butcan also be added to retard undesirable side reactions. Suitablepromoters for the processes of the invention include metals selectedfrom tin, zinc, copper, gold, silver, and combinations thereof. Thepreferred metal promoter is tin. Other promoters that can be used areelements selected from Group 1 and Group 2 of the Periodic Table.

The catalyst may be supported or unsupported. A supported catalyst isone in which the active catalyst agent is deposited on a supportmaterial by a number of methods, such as spraying, soaking or physicalmixing, followed by drying, calcination, and if necessary, activationthrough methods such as reduction or oxidation. Materials frequentlyused as a support are porous solids with high total surface areas(external and internal) which can provide high concentrations of activesites per unit weight of catalyst. The catalyst support may enhance thefunction of the catalyst agent. A supported metal catalyst is asupported catalyst in which the catalyst agent is a metal.

A catalyst that is not supported on a catalyst support material is anunsupported catalyst. An unsupported catalyst may be platinum black or aRaney® (W.R. Grace & Co., Columbia, Md.) catalyst. Raney® catalysts havea high surface area due to selectively leaching an alloy containing theactive metal(s) and a leachable metal (usually aluminum). Raney®catalysts have high activity due to the higher specific area and allowthe use of lower temperatures in hydrogenation reactions. The activemetals of Raney® catalysts include nickel, copper, cobalt, iron,rhodium, ruthenium, rhenium, osmium, iridium, platinum, palladium;compounds thereof; and combinations thereof.

Promoter metals may also be added to the base Raney® metals to affectselectivity and/or activity of the Raney® catalyst. Promoter metals forRaney® catalysts may be selected from transition metals from Groups IIIAthrough VIIIA, IB and IIB of the Periodic Table of the Elements.Examples of promoter metals include chromium, molybdenum, platinum,rhodium, ruthenium, osmium, and palladium, typically at about 2% byweight of the total metal.

The catalyst support useful herein can be any solid, inert substanceincluding, but not limited to, oxides such as silica, alumina andtitania; barium sulfate; calcium carbonate; and carbons. The catalystsupport can be in the form of powder, granules, pellets, or the like.

A preferred support material of the invention is selected from the groupconsisting of carbon, alumina, silica, silica-alumina, silica-titania,titania, titania-alumina, barium sulfate, calcium carbonate, strontiumcarbonate, compounds thereof and combinations thereof. Supported metalcatalysts can also have supporting materials made from one or morecompounds. More preferred supports are carbon, titania and alumina.Further preferred supports are carbons with a surface area greater than100 m²/g. A further preferred support is carbon with a surface areagreater than 200 m²/g. Preferably, the carbon has an ash content that isless than 5% by weight of the catalyst support; the ash content is theinorganic residue (expressed as a percentage of the original weight ofthe carbon) which remains after incineration of the carbon.

The preferred content of the metal catalyst in the supported catalyst isfrom about 0.1% to about 20% of the supported catalyst based on metalcatalyst weight plus the support weight. A more preferred metal catalystcontent range is from about 1% to about 10% of the supported catalyst.

Combinations of metal catalyst and support system may include any one ofthe metals referred to herein with any of the supports referred toherein. Preferred combinations of metal catalyst and support includepalladium on carbon, palladium on calcium carbonate, palladium on bariumsulfate, palladium on alumina, palladium on titania, platinum on carbon,platinum on alumina, platinum on silica, iridium on silica, iridium oncarbon, iridium on alumina, rhodium on carbon, rhodium on silica,rhodium on alumina, nickel on carbon, nickel on alumina, nickel onsilica, rhenium on carbon, rhenium on silica, rhenium on alumina,ruthenium on carbon, ruthenium on alumina and ruthenium on silica.

Further preferred combinations of metal catalyst and support includepalladium on carbon, palladium on alumina, palladium on titania,platinum on carbon, platinum on alumina, rhodium on carbon, rhodium onalumina, ruthenium on carbon and ruthenium on alumina.

Suitable diamines for Reaction (I) may be obtained commercially from,for example, Huntsman (Houston, Tex.) or BASF (Mount Olive, N.J.), ormay be synthesized by methods well known to those skilled in the art.For a discussion of the synthesis of diamines, see, for example, Eller,K. and Henkes, E., Diamines and Polyamines (Ullmanns Encyclopedia ofIndustrial Chemistry (2002) Wiley-VCH Verlag GmbH & Co, Chapter 8) andExperimental Methods in Organic Chemistry, 3^(rd) Edition (Moore, J.,Dalrymple, D. and Rodig, O. (eds.) (1982) Saunders College Publishing,NY, Chapter 22. Suitable diamines are those having the FormulaR²R³N-Z-NH₂ wherein Z is —(CH₂)_(n)—, wherein n is an integer from 2 to12 and R² and R³ taken independently are H, —CH₃, —CH₂CH₃ or C₃ to C₆straight-chain or branched monovalent alkyl.

The formation of pyrrolidine-2-ones may be carried out in batch,sequential batch (i.e., a series of batch reactors) or in continuousmode in any of the equipment customarily employed for continuous process(see for example, H. S. Fogler, Elementary Chemical ReactionEngineering, Prentice-Hall, Inc., N.J., USA).

The pyrrolidinones synthesized according to Reaction (I) may berecovered, for example, by distillation, or by filtration to removesolid acid catalyst particles if present.

Conversion of a Pyrrolidine-2-one to a Composition of the PresentInvention

A composition of the present invention may be synthesized byquaternizing the non-ring nitrogen of the pyrrolidine-2-one to obtain aquaternary ammonium compound of the Formula:

wherein Z is —(CH₂)_(n)— wherein n is an integer from 2 to 12, R², R³,and R⁴ taken independently are —CH₃, —CH₂CH₃ or C₃ to C₆ straight-chainor branched monovalent alkyl, and A- is selected from the groupconsisting of Cl⁻, Br⁻, and I⁻.

In order to form a quaternary ammonium compound, the pyrrolidine-2-oneis contacted with an alkylating halide having the Formula R¹-A whereinR¹ is selected from the group consisting of —CH₃, —CH₂CH₃ or C₃ to C₈straight-chain or branched monovalent alkyl, and A⁻ is selected from thegroup consisting of Cl⁻, Br⁻, and I⁻. Methods for performingquaternization reactions are well-known and are described in OrganicChemistry (Morrison and Boyd (ed.) 3^(rd) Edition (1973) Allyn andBacon, Inc., Boston, Chapter 23.5, pages 752-753).

The quaternization reaction may optionally be carried out in an inertsolvent, such as acetonitrile, acetone or dichloromethane. Thequaternization may be accomplished by refluxing of the reactants,optionally under an inert atmosphere. When the compositions of thepresent invention and/or the reactants used for synthesis of thecompositions are hygroscopic, it is preferable to carry out thequaternization and/or anion exchange reaction (see below) underconditions that exclude water and air. The alkylating halide is presentin slight excess (ca. 5%) at the start of the reaction. The reaction iscarried out at a temperature of from about 10 degrees C. to about 80degrees C.; the reaction is preferably carried out at a temperature offrom about 30 degrees C. to about 70 degrees C., more preferably fromabout 60 degrees C. to about 70 degrees C. The time for the reaction isgenerally from about 1 minute to about 48 hours; the time for thereaction is preferably from about 30 minutes to about 24 hours.

Anion Exchange

The compositions of the present invention are expected to be liquid atroom temperature, making it appropriate to refer to them as “ionicliquids.” However, if they are not liquid at room temperature it may bepossible to convert them to a liquid by substituting a different anion,i.e., A⁻, by an anion exchange reaction. Thus, the quaternary ammoniumcomposition may be further contacted with M⁺A⁻, wherein M is selectedfrom the group consisting of H, Li, K, Na, Ag, Mg, Ca, Ce, Ba, Rb andSr, and A⁻ is an anion selected from the group consisting of [BF₄]⁻,[PF₆]⁻, [SbF₆]⁻, [CH₃CO₂]⁻, [HSO₄]⁻, [NO₃]⁻, [CF₃SO₃]⁻, [HCF₂CF₂SO₃]⁻,[CF₃HFCCF₂SO₃]⁻, [HCClFCF₂SO₃]⁻, [(CF₃SO₂)₂N]⁻, [AlCl₄]⁻, [CF₃CO₂]⁻,[NO₃]⁻, [SO₄]²⁻, Cl⁻, Br⁻, I⁻ and F⁻, to form a composition having thedesired anion. Prior to the exchange reaction, excess alkylating agentmay be removed, for example, by evaporation. In addition, the quaternaryammonium compound may be washed with a solvent and dried prior to theanion exchange reaction. The anion exchange reaction may be carried outby mixing the quaternary ammonium compound with M⁺A⁻, optionally underan inert atmosphere. The anion exchange reaction may be carried out at atemperature of from about −20 degrees C. to about 100 degrees C. for atime of about 1 second to about 72 hours. Solvents useful in thereaction should be inert to the reactants and products, and includemethanol, ethanol, acetone and acetonitrile. Choice of the appropriatesolvent or mixture of solvents will allow for separation of thecomposition comprising the desired anion from the composition comprisingthe less desired anion as is well known in the art and as is shownherein in Example 2(b). Additional techniques may be utilized to enhancethe anion exchange reaction, such as ultrasonication as taught in WO03/048078.

The composition comprising the desired anion can be recovered by asuitable technique such as evaporation of the reaction solvent underreduced pressure, decantation and/or filtration to remove precipitatedsalts.

Compositions (ionic liquids) of the present invention can be utilized inone phase systems or multiple phase systems as solvents or, perhaps, ascatalysts. The physical and chemical properties of the compositions(ionic liquids) of the present invention can be specifically selected bychoice of the appropriate cation and anion. For example, increasing thechain length of one or more alkyl chains of the cation will affectproperties such as the melting point, hydrophilicity/lipophilicity,density and solvation strength of the ionic liquid. Choice of the anioncan affect, for example, the melting point, the water solubility and theacidity and coordination properties of the composition. Thus it may bedesirable to perform an anion exchange reaction by contacting thecomposition with M⁺A⁻ as described above to replace a less desirableanion of an ionic liquid with an anion that gives the desired chemicaland physical properties for the ionic liquid composition. Effects ofcation and anion on the physical and chemical properties of ionicliquids are known to those skilled in the art and are reviewed in detailby Wassersheid and Keim (Angew. Chem. Int. Ed, supra) and Sheldon (Chem.Commun., supra).

Alkylation of Aromatic Compounds with Monoolefins

In one embodiment of the present invention, compositions of theinvention are useful as solvents for the production of at least onealkylated aromatic compound of the Formula:

wherein:

-   -   a) Q¹ is H, —CH₃, —C₂H₅, or CH₃—CH—CH₃;    -   b) Q² is H, —CH₃ or —C₂H₅; and    -   c) Q³ is —C₂H₅ or C₃ to C₁₈ straight chain alkyl group having        therein a single CH group, the carbon atom of which is bonded to        the aromatic compound.

In one embodiment of the invention, Q¹ and Q² are both H.

Alkylated aromatic compounds have many industrial uses, including asintermediates in styrene production, cumene production and surfactantsynthesis.

The production of at least one alkylated aromatic compound is carriedout by a process comprising:

-   -   (1) reacting a C₂ to C₁₈ straight-chain monoolefin with an        aromatic compound of the Formula:        wherein Q¹ and Q² are as defined above;        in an ionic liquid of the Formula:

wherein:

-   -   (i) Z is —(CH₂)_(n)—, wherein n is an integer from 2 to 12;    -   (ii) R², R³ and R⁴ taken independently are H, —CH₃, —CH₂CH₃ or        C₃ to C₆ straight-chain or branched monovalent alkyl; and    -   (iv) A⁻ is an anion selected from the group consisting of        [BF₄]⁻, [PF₆]⁻, [SbF₆]⁻, [CH₃CO₂]⁻, [HSO₄]⁻, [CF₃SO₃]⁻,        [HCF₂CF₂SO₃]⁻, [CF₃HFCCF₂SO₃]⁻, [HCClFCF₂SO₃]⁻, [(CF₃SO₂)₂N]⁻,        [AlCl₄]⁻, [CF₃CO₂]⁻, [NO₃]⁻, [SO₄]²⁻, Cl⁻, Br⁻, I⁻, and F⁻;        in the presence of an acid catalyst that is soluble in the ionic        liquid, and    -   (2) separating the organic phase comprising the at least one        alkylated aromatic compound from the ionic liquid phase.

The alkylation reaction yields a mixture of products. Thus, the organicphase of step (2) comprises a product mixture comprising at least onealkylated aromatic compound of the Formula:

wherein Q¹, Q² and Q³ are as defined above.

The acid catalyst is a homogeneous acid catalyst such as CF₃SO₃H,HCF₂CF₂SO₃H, AlCl₃, HF, H₂SO₄, H₃PO₄ or HCl. The acid catalyst is usedat a concentration from about 0.01% to about 10% by weight of thereaction solution comprising the aromatic compound, the monoolefin andthe ionic liquid.

The aromatic compound is benzene or a benzene-derivative, such astoluene, xylene, ethyl benzene or isopropyl benzene.

The ionic liquid comprises from about 1% to about 75% by weight of thereaction solution.

The reaction is carried out at a temperature between about 25 degrees C.and about 200 degrees C., and a pressure between atmospheric pressureand that pressure required to maintain the reactants in a liquid state.In one embodiment of the invention, the reaction is carried out at about25 degrees C. at pressure is atmospheric pressure.

At the start of the reaction the aromatic compound is in molar excessrelative to the monoolefin. In one embodiment, the molar ratio of thearomatic compound to the monoolefin at the start of the reaction isabout 8:1.

An advantage to the use of an ionic liquid in this reaction is that thereaction product comprises an organic phase that comprises the at leastone alkyl aromatic compound and an ionic liquid phase that comprises theacid catalyst. Thus the at least one alkyl aromatic compound in theorganic phase is easily recoverable from the acid catalyst by, forexample, decantation. The acid catalyst in the ionic liquid may berecycled and used in subsequent reactions.

The aromatic alkylation reaction may be carried out in batch, sequentialbatch (i.e., a series of batch reactors) or in continuous mode in any ofthe equipment customarily employed for continuous process (see forexample, H. S. Fogler, Elementary Chemical Reaction Engineering,Prentice-Hall, Inc., N.J., USA). One skilled in the art will recognizethat at higher temperatures or pressures a sealed vessel or pressurevessel is required.

EXAMPLES

The following abbreviations are used:

Nuclear magnetic resonance is abbreviated NMR; thermogravimetricanalysis is abbreviated TGA, gas chromatography is abbreviated GC; gaschromatography-mass spectrometry is abbreviated GC-MS; thin layerchromatography is abbreviated TLC. Centigrade is abbreviated C, megaPascal is abbreviated MPa, gram is abbreviated “g”, milliliter isabbreviated “ml”, hour is abbreviated “hr”.

ESCAT-142 (Pd/C catalyst) was obtained from Engelhard Corp. (Iselin,N.J.). Ethyl levulinate and N,N-dimethylethylenediamine were obtainedfrom Alfa Aesar (Ward Hill, Mass.). Acetonitrile, iodopropane,bromopropane, bromopentane, ethanol, sodium hydroxide, triflic acid,potassium triflate, 1-dodecene, p-xylene,bis-trifluoromethanesulfonimide, and bis-hexafluorophosphate wereobtained from Sigma-Aldrich (St. Louis, Mo.).

Example 1 Preparation of the Bis-Trifluoromethanesulfonimide Salt of1-(2-N,N,N-Dimethylpropylaminoethyl)-5-Methyl-Pyrrolidine-2-one a)Preparation of 1-(2-N,N-Dimethylaminoethyl)-5-Methyl-Pyrrolidine-2-one

Ethyl levulinate (18.5 g), N,N-dimethylethylenediamine (11.3 g), and 5%Pd/C (ESCAT-142, 1.0 g) were mixed in a 400 ml shaker tube reactor. Thereaction was carried out at 150 degrees C. for 8 hr under 6.9 MPa of H₂.

The reactants and products were analyzed by gas chromatography on aHP-6890 GC (Agilent Technologies; Palo Alto, Calif.) and HP-5972A GC-MSdetector equipped with a 25M×0.25 MM ID CP-Wax 58 (FFAP) column. The GCyields were obtained by adding methoxyethyl ether as the internalstandard. The ethyl levulinate conversion was 99.7%, and the productselectivity for 1-(2-N,N-dimethylaminoethyl)-5-methyl-pyrrolidine-2-onewas 98.6%.

b) Preparation of the Iodide Salt of1-(2-N,N,N-Dimethylpropylaminoethyl)-5-Methyl-Pyrrolidine-2-one

For the quaternization reaction, purified1-(2-N,N-dimethylaminoethyl)-5-methyl-pyrrolidine-2-one (1.7 g) wasplaced in 5 g of dry acetonitrile, and 1.69 g of 1-iodopropane wasadded. This mixture was refluxed overnight under a nitrogen atmosphere;the reaction was shown to be complete via TLC, yielding the iodide saltof the quaternary ammonium compound. The acetonitrile was then removedunder vacuum.

c) Preparation of the Bis-Trifluoromethanesulfonimide Salt of1-(2-N,N,N-Dimethylpropylaminoethyl)-5-Methyl-Pyrrolidine-2-one by AnionExchange

For the anion exchange reaction, the iodide salt (1 g) produced in thequaternization reaction of step (b) was added to water (5 g), and thenethanol (5 g) was added. A stoichiometric amount ofbis-trifluoromethanesulfonimide was added and the mixture was stirredfor about 24 hours under nitrogen. A separate layer formed at thebottom, orange-red in color, which was quickly washed with water; theupper layer was decanted. The orange-red liquid was then placed in anoven at 100 degrees C. under vacuum for 48 hours to obtain the ionicliquid (bis-trifluoromethanesulfonimide salt of1-(2-N,N,N-dimethylpropylaminoethyl)-5-methyl-pyrrolidine-2-one). Thestability of the ionic liquid was investigated by thermogravimetricanalysis as follows: the ionic liquid (79 mg) was heated at 10 degreesC. per minute up to 800 degrees C. using a Universal V3.9A TA instrumentanalyser (TA Instruments, Inc., Newcastle, Del.); the resultsdemonstrated that the ionic liquid is stable to decomposition up toabout 300 degrees C.

Example 2 Preparation of the Hexafluorophosphate Salt of1-(2-N,N,N-Dimethylpropylaminoethyl)-5-Methyl-Pyrrolidine-2-one a)Preparation of the Bromide Salt of1-(2-N,N,N-Dimethylpropylaminoethyl)-5-Methyl-Pyrrolidine-2-one

For the quaternization reaction purified1-(2-N,N-dimethylaminoethyl)-5-methyl-pyrrolidine-2-one (1 g)synthesized in Example 1 was placed in 5 g of dry acetonitrile, and 0.71g of 1-bromopropane was added. This mixture was refluxed overnight undera nitrogen atmosphere; the reaction was shown to be complete via TLC,yielding the bromide salt of the quaternary ammonium compound. Theacetonitrile was then removed under vacuum.

b) Preparation of the Hexafluorophosphate Salt of1-(2-N,N,N-Dimethylpropylaminoethyl)-5-Methyl-Pyrrolidine-2-one by AnionExchange

For the anion exchange reaction, the bromide salt (0.5 g) produced inthe quaternization reaction of Example 2(a) was added to water (5 g),and then ethanol (5 g) was added. A stoichiometric amount ofbis-hexafluorophosphate (Sigma-Aldrich) was added, followed by anadditional 2 ml of water, and the mixture was stirred for about 24 hoursunder nitrogen. A separate layer formed at the bottom, which was quicklywashed with water; the upper layer was decanted. The remaining liquidwas then placed in an oven at 100 degrees C. under vacuum for 48 hoursto obtain the ionic liquid; 0.6 g of the ionic liquid was obtained.

Example 3 Preparation of the Bromide Salt of1-(2-N,N,N-Dimethylpentylaminoethyl)-5-Methyl-Pyrrolidine-2-one a)Preparation of the Bromide Salt of1-(2-N,N,N-Dimethylpentylaminoethyl)-5-Methyl-Pyrrolidine-2-one

For the quaternization reaction purified1-(2-N,N-dimethylaminoethyl)-5-methyl-pyrrolidine-2-one (1 g)synthesized in Example 1 (a) was placed in 5 g of dry acetonitrile, and1.51 g of 1-bromopentane was added. This mixture was refluxed overnightunder a nitrogen atmosphere; the reaction was shown to be complete viaTLC, yielding the bromide salt of the quaternary ammonium compound. Theacetonitrile was then removed under vacuum, yielding the ionic liquid.

b) Preparation of the Trifluoromethylsulfonate Salt of1-(2-N,N,N-Dimethylpentylaminoethyl)-5-Methyl-Pyrrolidine-2-one

For the quaternization reaction, purified1-(2-N,N-dimethylaminoethyl)-5-methyl-pyrrolidine-2-one (13.5 g) fromstep (a) was placed in 20 g of dry acetonitrile, and 10 g of1-bromopropane was added. The mixture was heated at 60 degrees C. for 4hours. Potassium triflate was then added in acetonitrile (9.5 g in 30 mlof acetonitrile). The mixture was stirred for 4 hours at 60 degrees C.and then left overnight at room temperature. The potassium bromideprecipitated. The mixture was filtered and the potassium bromide-freesolid was placed under vacuum to remove the solvent. The mixture wasdried to give the trifluoromethanesulfonate as the anion of the ionicliquid. The product was confirmed by NMR. The final yield of the ionicliquid (trifluoromethylsulfonate salt of1-(2-N,N,N-dimethylpentylaminoethyl)-5-methyl-pyrrolidine-2-one) was 13g.

Example 4 Alkylation of Xylene with Dodecene Using an Ionic Liquid asSolvent

p-Xylene (5 g) was added to 1.67 g of 1-dodecene. The ionic liquidproduced in Example 1(b) (iodide salt of1-(2-N,N,N-dimethylpropylaminoethyl)-5-methyl-pyrrolidine-2-one; 1.8 g)containing 0.25 g of triflic acid as catalyst was added to thexylene/dodecene mixture. The two-phase system was heated to 100 degreesC. and stirred for 1 hour. GC analysis demonstrated that greater than80% of the alkylated product was obtained, with only 20% of the dodeceneun-reacted. The solution was cooled and the reaction product wasdecanted from the brown colored ionic liquid/acid catalyst phase. Theorganic phase was rapidly stirred with 30 ml of water and the acidcontent was determined; 0.45 g of 0.01 M NaOH was needed to neutralizethe acid which is consistent with >99.8% retention of the acid in theionic liquid (separate) phase.

The reaction produced a mixture of products as shown by GC analysis. Oneof the products synthesized by the reaction had the Formula:

1. A compound of the Formula:

wherein: (i) Z is —(CH₂)_(n)—, wherein n is an integer from 2 to 12;(ii) R², R³ and R⁴ taken independently am H, —CH₃, —CH₂CH₃ or C₃ to C₆straight-chain or branched monovalent alkyl; and (iii) A⁻ is an anionselected from the group consisting of [BF₄]⁻, [PF₆]⁻, [SbF₆]⁻,[CH₃CO₂]⁻, [HSO₄]⁻, [CF₃SO₃]⁻, [HCF₂CF₂SO₃]⁻, [CF₃HFCCF₂SO₃]⁻,[HCClFCF₂SO₃]⁻, [(CF₃SO₂)₂N]⁻, [AlCl₄]⁻, [CF₃CO₂]⁻, [NO₃]⁻, [SO₄]²⁻,Cl⁻, Br⁻, I⁻, and F⁻.
 2. The compound of claim 1 wherein Z is—(CH₂)_(n)—, wherein n is an integer from 2 to
 6. 3. The compound ofclaim 1 wherein the anion is [PF₈]⁻, [HCF₂CF₂SO₃]⁻, [CF₃HFCCF₂SO₃]⁻,[HCClFCF₂SO₃]⁻ or [(CF₃SO₂)₂N]⁻.
 4. The compound of claim 2 wherein theanion is [PF₆]⁻, [HCF₂CF₂SO₃]⁻, [CF₃HFCCF₂SO₃]⁻, [HCClFCF₂SO₃]⁻ or[(CF₃SO₂)₂N]⁻.